motion blur w/ d800

Was testing d800 w/ 50mm 1.8g w/ A mode. Got a lot of motion blurs in capturing moving person even in a sun-lit room. Want to get your tips and thoughts re how to deal with it.

Do you set "minimum shutter speed" in the ISO setting menu to something fast (like 1/250)? I find that helps, but I am not sure it is best thing to do because it jacks ISO high for all pictures, even when I am photographing stills. Should I assign a button for it, and turn it on when I capture moving persons?